Decadal (1994–2008) change in the carbon isotope ratio in the eastern South Pacific Ocean. Issue 8 (1st August 2014)

• Record Type: Journal Article
• Authors: Ko, Young Ho; Lee, Kitack; Quay, Paul D.; Feely, Richard A.
• Is Part Of: Global biogeochemical cycles. Volume 28:Issue 8(2014:Aug.)
• Page Start: 775
• Page End: 785
• Publication Date: 2014-08-01
• Subjects: Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/2013GB004786
• Languages: English
• ISSNs: 0886-6236

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>We determined the 14 year change in the anthropogenic CO<sub>2</sub> inventory in the eastern South Pacific Ocean along the 110°W meridian from 67°S to 21°N, using seawater δ<sup>13</sup>C data sets collected in 1994 and 2008. The vertical integral of the 14 year δ<sup>13</sup>C change was assessed in five latitude bands and found to be greatest (−14.7‰ m yr<sup>−1</sup>) in the subpolar band (38°S–55°S) and smallest (−3.0‰ m yr<sup>−1</sup>) in the tropical band (21°N–18°S). The δ<sup>13</sup>C change in each of the latitudinal bands was primarily caused by inputs of anthropogenic CO<sub>2</sub> via air‐sea exchange and transport. More than 50% of the total anthropogenic CO<sub>2</sub> was added to the subpolar band via the northward movement of Antarctic Intermediate Water (AAIW) from the south, and the remaining 50% was added via air‐sea exchange. We also calculated the ratio of the temporal change in δ<sup>13</sup>C to the change in dissolved inorganic carbon, which is a measure of the efficiency of oceanic uptake of anthropogenic CO<sub>2</sub>. The ratio for AAIW in 1994 (−0.017‰ (µmol kg<sup>−1</sup>) <sup>−1</sup>) was greater than that in 2008 (−0.010‰ (µmol kg<sup>−1</sup>) <sup>−1</sup>) based on the change in preformed δ<sup>13</sup>C and dissolved inorganic carbon (DIC), indicating reduced efficiency of CO<sub>2</sub> uptake by the Southern Ocean in 2008 relative to that in 1994. AAIW remained at the surface for a shorter period in 2008 relative to 1994, and thus would have taken up less atmospheric CO<sub>2</sub> prior to subduction. The projected reduction in this ratio indicates a weakening of CO<sub>2</sub> uptake by the Southern Ocean in the future.</p> </abstract>